SK69798A3 - A soft, bulky absorbent paper containing chemithermomechanical pulp - Google Patents

Abstract

Soft, bulky, absorbent paper containing at least 20 percent by weight of a high-temperature chemithermomechanical pulp (HT-CTMP), calculated on the total fibre weight. The paper also contains at least 10 percent by weight pulp that exhibits good strength properties, such as chemical pulp and/or recycled fibre pulp, and has a bulk of at least 5.5 cm<3>/g. The bulk, absorption and liquid-dispersion properties of the paper are enhanced by admixing HT-CTMP with the paper pulp.

Description

FINE, VOLUME ABSORPTION PAPER CONTAINING CHEMICAL-THERMOMECHANIC PROCESSED PAPER

Technical field

The present invention provides a fine bulk absorbent paper. Fine paper or tissue paper, which is commonly used for the manufacture of household paper products, toilet paper, wipes, paper handkerchiefs, etc. it can be made from a variety of different types of cellulose fibers.

BACKGROUND OF THE INVENTION

Disregarding recycled pulp, which is currently widely used mainly in the manufacture of toilet paper and household paper, and focusing only on the use of primary fibers, chemical pulp is the most common type of pulp used in fine paper. Chemical pulp is made by impregnating wood chips with chemicals and then cooking the chips, during which the lignin, resin and hemicelluloses present are processed into the liquid used. After the brewing process is completed, the stock is passed through a screen and washed before it is whitened. This pulp contains no lignin, but only the fiber that contains pure cellulose is relatively light and. pliable. Depending on the properties of the wood used, the chemical pulp may contain both long fibers and short fibers, and may be both sulphate type and sulphite type pulp depending on the composition of the cooking liquid. Long-fiber chemical pulp, in particular sulphate-type pulp, has a beneficial effect on the strength properties of the fine paper with respect to both dry and wet strength.

Chemical pulp is unprofitable because it provides a yield of only about 50% calculated on the initial wood material. Thus, the paper pulp is relatively expensive. As a result, a less expensive so-called &quot; high-yield pulp, e.g. mechanical or thermo-mechanical pulp; with this in mind, see

GB Patent Specification 1, 533, 045. The mechanical pulp is made by crushing or refining the initial wood material. The principle applied in the production of mechanical pulp is based on the mechanical crushing of wood species. All wood material is utilized, and the lignin thus remains in fibers that are real short and stiff. Thermomechanical pulp (TMP) is made by refining wood in disc refiners at increasing steam pressure. Lignin also remains in the fibers of thermo-mechanical pulp.

Chemical-thermomechanical pulp (CTMP) is a specification of thermomechanical pulp modified by the supply of small quantities of chemical substances, usually sulphites, which are supplied prior to the subsequent refining process. The admixture of a specified amount of thermo-mechanical pulp in fine paper has a positive effect on properties such as bulkiness and absorption.

For the manufacture of fine paper, all of the above types of pulp are currently used.

SUMMARY OF THE INVENTION

It is an object of the present invention to produce fine paper whose properties are further improved in terms of volume and absorption. This objective was achieved by including at least 20% by weight, calculated on the total fiber weight, of high temperature chemical thermo-mechanical pulp (HT-CTMP) paper, showing the following characteristics: long fiber content between 60% and 75% (fibers, which have been retained on a 30 mesh mesh screen) fractionated in accordance with Bauer McNett, a fine material content of not more than 14% (fibers which have passed through a 200 mesh mesh screen) f rakcinated in accordance with Bauer McNett, the lowest drainage rate of 600 ml CSF, a fiber lump content of less than 0.5%, preferably less than 0.25%, and a tensile index of at least 10 kNm / kg, the paper also comprising at least 10% by weight of the pulp having good strength properties, e.g. mechanical pulp and / or recycled pulp.

Surprisingly, it has been found that admixture of at least 20% HT-CTPT yields a paper of much larger volume than that obtained by the corresponding amount of admixture of conventional CTMP. The absorption and proportion of the liquid dispersion improved. dispersion paper

The properties of the paper into the paper pulp as well and the quality of the liquid by increasing the amount of admixture by supplying HT-CTMP volume, the absorption

HT-CTMP delivered to the paper slurry.

The admixture of at least preferably long-fiber paper of desired strength can be good strength properties of recycled fibers. They can e.g. mechanical pulp, short-fiber chemical pulp,

10% pulp properties.

also obtained by the use of strength chemical pulp, sulphate type, adds the required strength, paper of other types to papers that have e.g. o pulps produced to also include other types of pulp, thermomechanical pulp, CTMP, etc.

The chemical pulp admixture in the paper was preferably ground with a dewatering resistance between 20-40 ° SR, more preferably 22-30 ° SR, while the HT-CTMP pulp was not milled or was milled at the lowest dewatering degree of 600 ml CSF.

The invention also relates to at least one layer comprising HT-CTMP and a fiber composition of at least so-called &quot; multi-ply paper, in at least 20% by weight of one additional layer, differs from the fiber composition of the above layer.

According to the invention, the paper should contain at least 20% by weight, calculated on the total weight of the pulp, of a high-temperature chemical-thermomechanical pulp of a given specific type, which is designated in the following as

HT-CTMP. This pulp and the method of its manufacture are described in Swedish Patent Application no. 9402101-1, the details of this application are included in the present part of the present invention. Characteristic features of this pulp are long fibers, high dewatering ability, a bulky, high yielding pulp having a low lump content on the fibers and a low content of fine material.

The pulp has a density of less than 400 kg / m ³ , preferably less than 325 kg / m ^3, and more preferably less than 275 kg / m ³ . Yield is greater than 88% and extract content less than 0.15%. The pulp has good strength properties - a tensile index of greater than 10 kNm / kg, preferably greater than 15 kNm / kg, and more preferably greater than 20 kNm / kg The fiber content in the fibers is very low - less than 0.5%, preferably less than 0, 25% and more preferably less than 0.10%. This pulp has a low content of fine material - not more than 14% by weight

ΒΜΝ <200 stitches (Tyler Standard), preferably not more than 10%. The long fiber content is high - between 60% and 75% according to BMN> 30 stitches, preferably between 62% to 72% and more preferably between 63% to 70%. The pulp has a high degree of dewatering - at least 600 ml CSF, preferably at least 650 ml CSF and more preferably at least 720 ml CSF.

The raw fiber material used to make the pulp may be any ligmocellulose containing materials e.g. wood or grass. From this point of view, a suitable material is soft wood, e.g. spruce.

The method applied in the manufacture of said pulp (HT-CTMP) differs from the standard methods used to make CTMP mainly by using a higher temperature in the impregnation, preheating and refining process, preferably at least 140 ° C. A note is made with respect to Sweden Patent Application no. 9402101-1 for a more detailed description of the method of manufacturing HT-CTMP pulp.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached figures are described in the following detailed description:

Figure 1 shows volume as a function of the level of individual CTMP and HT-CTMP impurities in paper pulp using two different HT-CTMP quality levels;

Figure 2 shows absorption as a function of the levels of individual CTMP and HT-CTMP impurities using two different HT-CTMP quality levels;

Figure 3 a-c shows the proportion of dispersion in the longitudinal, transverse and vertical directions of the paper as a function of the level of individual impurities of CTMP and HT-CTMP using two different HT-CTMP quality levels;

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention of this range (HT-CTMP affects paper properties compared to standard types of CTMP), a variety of tests were performed in which different amounts of HT-CTMP and CTMP were mixed into paper pulp. The sulphate-type long-fiber chemical pulp was used as an additional paper pulp in all tests. HT-CTMP pulp and CTMP pulp were mixed in amounts corresponding to 20%, 40%, 54% and 60% by weight, calculated on the total weight of the pulp. The CTMP used was obtained from Östrand and had a bulk density of approximately 2.7 cm ³ / g, a drainage rate of 500 ml CSF, a lump fiber content (Sommerville) of 0.1%, a tensile index of approximately 28 kN / kg, a long fiber content according to Bauer McNett (> 30 stitches) about 62%, Bauer McNett short fiber content (<200 stitches) about 15%, and a burst index of about 9.5 m ² / kg.

Two different levels of quality I and II were used, quality I had a larger volume. The HT-CTMP I had a volume of 4.25 cm ³ / g, a drainage rate of 735 ml CSF, a fiber lump content (Sommerville) of 0.36%, a tensile index of 14 kNm / kg, a long fiber content according to Bauer McNett (> 30 stitches) 71%, Bauer McNett short fiber content (<200 stitches) 9%, and tear index 6 m ² / kg.

The HT-CTMP II had a volume of 3.0 cm ³ / g, a drainage rate of 650 ml CSF, a lump content of fibers (Sommerville) of 0.1%, a tensile index of 22 kNm / kg, a long fiber content of Bauer McNett (> 30 eyes) 65.5%, Bauer McNett short fiber content (<200 stitches) 9%, and tear index 9 m ² / kg.

The sample paper used was made of pure chemical long-fiber sulphate-type paper, Munksi TCF-80, which was ground at a dewatering degree of between about 20 ° R and 26 ° R. The crushing process was performed at a constant power calculated per tonne of paper produced, indicating that the chemical fibers were crushed or refined to a greater degree per kilogram at lower levels of chemical pulp admixture. All parameters were kept constant throughout the assay except for the amount of CTMP and HT-CTMP mixed into the paper pulp. The amount of atomized chemicals delivered in combination with the crepe paper was determined to obtain proper adhesion in the Yankee cylinder.

Tests were made by preparing a stock of fiber with a consistency in the headbox ranging from 0.1% to 0.3% based on the dry fiber weight. A wet strength agent was also added to the fiber stock. The stock was supplied to the headbox of the wipe making machine and a paper web was formed on the reel. The formed paper web was dewatered, pre-dried and transferred to a Yankee roller where it was further dried before it was creped on the roller with a paint knife.

A person skilled in the art will know that paper towels can be made on different types of paper machine, and creping of paper to obtain the desired softness can be changed by techniques such as e.g. air drying. It will be understood that all processes by which paper towels can be manufactured in accordance with the invention are included in the present patent application document.

The formed dry paper web prior to creping will have an optimal weight per unit area of 12 to 30 g / m ² and, after creping, its weight per unit area will be 16 to 45 g / m ² .

The quality of the paper produced was measured with respect to unit weight of area, thickness, volume, dry and wet strength, absorption and liquid dispersion ratio, and the values obtained were reported in Tables 1-3 below. Quality was determined by standard SCAN or SIS methods, which are listed in the following tables. The measurement values given in the tables are the average values obtained by measuring three different samples.

Table 1 shows the weight per unit area, thickness and volume of paper produced with different levels of CTMP and two different HT-CTMP quality levels blended into paper pulp. Paper made from pure chemical pulp is used as a sample.

TABLE 1

The stock Level of admixture Weight per unit area [g / m ² ] Thickness [um] Volume [cm ³ / g] sample 29.4 14 8 5.1 CTMP 20% 29.4 166 5.7 _ 11 _ 40% 29.2 169 5.8 11 _ 60% 29.4 183 6.3 HT-CTMP 1 20% 29.6 168 5.7 II 40% 29.7 2 08 7.1 II 54% 30.0 248 8.3 _ 11 _ 60% 29.0 227 7.8 HT-CTMP 2 20% 30.2 168 5.6 _ II _ 40% 29.9 198 6.6 _ 11 _ 60% 29.4 224 7.6 method SCAN-P6: 75 SCAN-P47: 83 Calc.

Figure 1 shows the volume as a function of the degree of addition of CTMP and individual HT-CTMP I and II. As can be seen from the figure, the volume of paper containing HT-CTMP is noticeably increased compared to paper containing standard CTMP in admixtures of approximately 20% or more. The highest volume increase was obtained using HT-CTMP 1.

Table 2 shows the dry strength and the wet strength of paper made with different levels of CTMP and HT-CTMP having two different quality levels. Paper made from pure chemical pulp is used as a sample.

TABLE 2

The stock Level of admixtures Dry strength MD N / m CD dry strength N / m MC / CD ratio Wet strength MD N / m Mokrá pevn. CD N / m sample 333 216 1.5 78 53 CTMP 20% 351 235 1.5 102 61 II 40% 368 228 1.7 89 60 _ II _ 60% 378 229 1.7 106 63 HT-CTMP 1 20% 349 220 1.6 99 56 _ H _ 40% 329 190 1.8 85 52 - II _ 54% 303 173 1.8 92 49 HT-CTMP 2 20% 355 235 1.5 91 56 11 _ 40% 369 210 1.8 100 59 II 60% 307 185 1.7 89 54 Approach SCANP44: 81 Scan- P44: 81 Calc. SCANP58: 86 SCANP58: 86

Table 3 shows the absorption and liquid dispersion (WAT) in the longitudinal (x), transverse (y) and vertical (z) directions of the paper produced with different degrees of CTMP admixture and two different HT-CTMP quality levels. Paper made from pure chemical pulp is used as a sample.

The stock Level of admixture Total and. water g / g WAT, xs / cm WAT, y s / cm WAT, z / cm sample 3.8 3.91 0.93 0.59 CTMP 20% 3.9 4.08 0.86 0.70 _ II 40% 4.1 4.15 0.85 0.83 II _ 60% 4.3 4.30 0.76 0.85 HT-CTMP 1 20% 3.9 3.35 0.77 0.53 _ II _ 40% 4.7 2.35 0.53 0.38 II 54% 4.9 1.94 0.40 0.38 _ II _ 60% 5.0 1, 89 0.61 0.45 HT-CTMP 2 20% 3.9 4.47 0.86 0.47 _ II _ 40% 4.4 2.92 0.64 0.50 II __ 60% 4.6 2.38 0.60 0.59 Approach

Figure 2 shows paper uptake as a function of the level of CTMP impurity and individual HT-CTMP I and II. The absorption of paper containing HT-CTMP increases with increasing degree of admixture more than the absorption of paper containing standard CTMP. Paper containing HT-CTMP I shows the highest absorption.

Figures 3 a-c show the proportions of the dispersion in the longitudinal, transverse and vertical directions of the paper as a function of the level of the impurity CTMP and the individual HT-CTMP I and II. The figure shows that the proportion of dispersion in the longitudinal direction of the paper (x direction) increases with increasing levels of HT-CTMP, especially HT-CTMP I, while the proportion of dispersion decreases with increasing level of CTMP. The proportion of dispersion increases in the transverse direction (y direction) with increasing levels of CTMP and HT-CTMP, although more with HT-CTMP, more particularly with HT-CTMP I. The proportion of dispersion in the vertical direction (z direction) decreases with increasing CTMP admixture level. This was generally constant for HT-CTMP II and noticeably increased with HT-CTMP I. A high dispersion ratio means more advantageous and faster use of the total paper absorption capacity and is therefore an important function.

Overall, an admixture of at least 20%, preferably 25% by weight of HT-CTMP in paper towels results in a surprisingly high quality improvement with respect to such important properties as volume, absorption and liquid dispersion capability. However, similarly to CTMP, the dry and wet strength of the paper decreases with increasing levels of HT-CTMP. In order to achieve acceptable strength values, it is recommended that the paper comprises at least 10% by weight, preferably at least 20% by weight of the stock having good strength properties, e.g. o chemical pulp or recycled fibrous pulp. The chemical pulp is preferably a sulphate type softwood pulp, but other types may also be used. fiber, e.g. mechanical pulp, thermomechanical pulp, CTMP, chemical short-fiber paper, etc. It should also be noted that soft paper containing more than 90% and even up to 100% HT-CTMP can be produced assuming lower paper strength values are acceptable.

The paper pulp contained in the paper is preferably ground with a dewatering resistance of between 20 ° to 45 ° SR, preferably between 22 ° to 30 ° SR, while the HT-CTMP pulp is not milled or milled at the lowest dewatering rate of 600 ml CSF. If two types of pulp, i. chemical pulp and HT-CTMP, together with necessarily the same resistance to dewatering, much of the improvement in volume and improved absorption properties of HT-CTMP is substantially lost.

For the manufacture of paper towels, it is known to use a multi-layer box and to use different types of pulp in different layers. In view of the good absorption and liquid dispersion capability of HT-CTMP, HT-CTMP may be present in the middle layer or layers, depending on the paper.

Where a high total absorption capacity is required in the above-mentioned different external properties to those originally required,

The HC-CTMP is optionally mixed with another pulp, e.g. chemical pulp, and. preferably, it will form a middle layer, while the outer layers will contain paper stock having good strength properties, e.g. chemical pulp and / or recycled pulp, preferably in an amount corresponding to at least 81% by weight and more preferably 85% by weight. The HT-CTMP is contained in the middle layer preferably in an amount corresponding to at least 20% by weight.

However, if a paper with a rapid absorption property is initially desired, the HT-CTMP is optionally blended e.g. With the paper pulp and / or recycled pulp and optimally present in the outer layers, the required strength of the middle layer will provide at least 81% by weight and more preferably at least 85% by weight of the pulp and / or recycled pulp. The HT-CTMP is present in the outer layers preferably in an amount corresponding to at least 20% by weight. Multilayer paper can also be formed using mixtures of other types of pulp, e.g. mechanical pulp, thermomechanical pulp, CTMP, short fiber chemical pulp, etc.

7 / -q ₍

Claims (6)

A soft bulk absorbent paper comprising a certain amount of a chemical-thermomechanical type of pulp. (CTMP), characterized in that it contains at least 20% by weight of high temperature chemical thermo-mechanical pulp (HT-CTMP), calculated on the total weight of pulp, which shows the following characteristics: Bauer McNett fractionated long fiber content between 60% and 75% % (fibers entrapped on a 30-mesh wire mesh), Bauer McNett fractionated fine material content not more than 14% (fibers passed through a 200-mesh wire mesh), the minimum drainage rate is 600 ml CSF, fiber content less than 0 5%, preferably less than 0.25% and a tensile index of at least 10 kNm / kg; this paper also contains at least 10% by weight of the sieve, which shows good strength properties, e.g. o chemical pulp and / or recycled pulp. Paper according to claim 1, characterized by a volume size of at least 5.5 cm ³ / g. Paper according to claim 1 or claim characterized by a recycled fiber content of up to 55% by weight. Paper according to one or more of the preceding claims, characterized by a chemical pulp content in the form of a sulphate-type softwood pulp. Paper according to one or more of the preceding claims, characterized by a chemical pulp content that has been ground to at least 20 ° SR, preferably 22 ° SR, against the dewatering, while the HT-CTMP contained in the paper is either unground or milled at the lowest dewatering rate of at least 600 ml CSF. Paper according to one or more of the preceding claims, characterized by a multilayer treatment in which at least one layer contains at least 20% by weight of HT-CTMP, and whose fiber composition of the at least one other layer differs from the foregoing layer.